Vacuum cleaners typically use a suction nozzle that is movable across a surface to be cleaned. The suction created at an inlet in the nozzle results in the removal of free dirt particles accumulated on the surface. However, ground in dirt is frequently encountered when cleaning carpets or other textured surfaces, and reliance on suction for removal of such ground-in dirt has proven to be unsatisfactory.
Accordingly, effort has been made to provide vacuum cleaners with an effective means to beat the carpet surface to dislodge ingrained dirt particles. Such beaters are often located on the vacuum cleaner nozzle head, so that dirt can be dislodged and instantly removed by simply moving the nozzle head across a soiled carpet surface. The earliest known beaters are mechanical beaters, which physically strike the carpet surface to loosen dirt particles.
An example of a mechanical beater is disclosed in U.S. Pat. No. 6,108,853 to Dittus, which includes a cylindrical rotatable beater brush having a plurality of extending resilient bristles and prongs that physically beat the carpet as the nozzle head is moved.
Another example is disclosed in U.S. Pat. No. 6,161,251 to Lee et al., which uses a mechanical vibration generating device that vibrates using air sucked though a supplementary suction hole to beat the carpet. In various embodiments, the vibration generating device can be used to vibrate the nozzle body which in turn vibrates the surface to be cleaned or the vibration generating device can directly beat the surface.
However, one disadvantage of a mechanical beater is damage to the surface being cleaned. Sonic beaters were developed, which rely on fluctuation in air flow through the nozzle opening to dislodge dirt particles. For example, U.S. Pat. No. 2,932,054 to Lichtgarn discloses a vacuum cleaner in which the vibration of disks produces a vibrating column of air that loosens dirt in a carpet. Similarly, U.S. Pat. No. 5,400,466 to Alderman et al. discloses an air vibration suction nozzle that includes a speaker that vibrates the suction air and a means for adjusting the frequency and amplitude of the airwaves produced by the speaker.
Although sonic beaters avoid physical damage to a carpet often caused by mechanical beaters, they are not as effective in dislodging dirt on the surface of a carpet pile. At the same time, mechanical beaters are not as effective in removing particles embedded deeply in the carpet pile. Also, mechanical beaters tend to push dirt particles down into the carpet, thereby making it more difficult to effectively clean the carpet.
U.S. Pat. Nos. 7,143,470 and 7,225,505, both to applicant, disclose vacuum cleaners having both mechanical and sonic beaters. However, such vacuum cleaners have a single suction inlet associated with the mechanical and sonic beaters. Thus, the dirt and debris loosened by the sonic beater is drawn in through the single suction inlet associated with the mechanical and sonic beaters. Additionally, these patents do not disclose a suction path through the sonic beater. Accordingly, a need exists for a vacuum cleaner having suction inlets at both the mechanical and the sonic beaters.